1. Field of the Invention
The present invention relates to an image forming unit in an image forming apparatus for forming an image by transferring a toner image.
2. Description of the Related Art
There has been known that in a conventional image forming apparatus, a transfer section including an image bearing body (i.e., a photosensitive body), a primary transfer roll, an intermediate transfer belt and the like is unified into an image forming unit, which unit is configured to be detachably attached to an image forming apparatus main body (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2003-195729). The image forming unit of this type is provided with a pair of side frames for rotatably supporting the primary transfer roll and a plurality of other rolls, wherein the intermediate transfer belt is slidably wound on the plurality of rolls so as to apply a predetermined tension to the rolls.
Furthermore, the plurality of rolls in the image forming unit include a secondary transfer backup roll for backing up secondary transfer by means of a secondary transfer roll. Specifically, the intermediate transfer belt wound around the secondary transfer backup roll and the secondary transfer roll hold a recording sheet therebetween, whereby a toner image, which has been primarily transferred onto the intermediate transfer belt, is secondarily-transerred onto the recording sheet.
Consequently, the secondary transfer roll is adapted to press the intermediate transfer belt wound around the secondary transfer backup roll by a significantly great pressing force. Therefore, there is a possibility that an inconvenience such as a deficient image quality or the like occurs unless the image forming unit is equipped with strength resistible to the pressing force.